According to the criminal warrant, Smith and Hebert smoked marijuana and then had an argument, which turned physical when Smith grabbed a kitchen knife and stabbed Hebert. Smith then chased Hebert outside the home, where witnesses described seeing the teen on top of Hebert, stabbing her multiple times.

Happening now: We’re inside a Cobb County courtroom where a negotiated plea has been reached in the stabbing death of Abbey Hebert. Her cousin, Olivia Smith, is accused of murder. We’re expecting emotional testimony. Live stream on @wsbtv. pic.twitter.com/eAxdHPBFTy

"There's no way to sugarcoat it. It was a brutal murder, without a shadow of a doubt," Hebert's father, Steve Hebert, said. "When you brutally stab another person, go after their face, to dismember them in a way, it's a jealous rage."

Smith was charged with felony murder, malice murder, aggravated assault and possession of a knife during the commission of the crime.

Prosecutor Jesse Evans said on the day of the stabbing, Smith told police that she and Hebert had smoked something prior to the stabbing and "God told her to go after Abbey."

“This was a jealous rage.” - Steve Hebert, father of 17-year old Abbey Hebert during his victim impact statement. Hebert says his daughter was stabbed 10-20 times in the face. Olivia Smith pleads guilty to a negotiated plea of voluntary manslaughter, 20 years in prison. @wsbtvpic.twitter.com/0Yr7AhUQhg

"There are no winners. There's only losers here and there's none greater than Abbey Hebert and her family," Evans said.

Tears flow during impact statements

During his victim impact statement, Steve Hebert spoke directly to Smith and her family in court, calling their actions appalling. Smith broke down once again and the judge had to stop Hebert to ask him to address the court and not individuals.

"None of us will be the same. It's not a grief that we live with on Nov. 14. It's a daily grief and we live with it every second of every day," Steve Hebert said.

"I stand before you today to speak on behalf of my sister's character," Hannah Smith said. "My sister is not a monster. Olivia loved Abbey. She would do anything for her ... Olivia and Abbey were best friends. They were family."

Hannah Smith said drugs were to blame for what happened that day.

"Abbey would not want Olivia to be confined to a cell for the rest of her life," she said. "She would understand that drugs took over Olivia ... Drugs have destroyed our family and our lives forever."

Abbey Hebert’s family wore this pin and bracelet in court this afternoon. Olivia Smith was sentenced to 20 years in prison. Emotional testimony from both families, Live at 6. @wsbtvpic.twitter.com/71pAn04Dp9